Ask The Vet: There are ways to prevent horses from west Nile virus infection

Monday

Oct 8, 2012 at 5:00 AM

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There has been much discussion these past few weeks regarding the recent outbreak of West Nile virus in the United States. There have been a multitude of cases in both humans and horses in several states across America this past month, ranging from California to Texas to Kentucky.

There have been 3,545 cases across the United States in humans -- the highest recorded number since 2003. The disease has spread from coast to coast, with new cases being reported daily. Unfortunately, people and horses in Ohio were not immune and the disease has made its way into our great state.

As of Sept. 27, there have been 93 reported human cases of West Nile virus in Ohio, with one positive found in Richland County. In terms of veterinary cases (horses), there have been nine reported cases, with one in Wayne County. More recent reports have shown that two horses have succumbed to the disease in Knox County this month. Reports also are showing that 42 counties have West Nile virus positive humans, mosquitoes and/or horses.

West Nile virus is spread by infected mosquitoes. Mosquitoes are infected after feeding off infected birds. The mosquitoes then feed on humans and other animals when they bite, thereby transferring the disease.

There certainly is seasonal activity to mosquitoes and the spread of West Nile, with most activity peaking in late September.

West Nile virus is a virus that causes encephalitis -- or infection in the brain and spinal cord, leading to neurologic signs in your horse. Signs and symptoms that horse owners should be aware of include loss of appetite, lethargy, fever, weakness in the hind end, incoordination, trouble swallowing, convulsions, circling, etc.

If your horse begins showing any of these signs, contacting your regular veterinarian is the first step in determining if West Nile virus is the cause, as many other diseases can cause similar symptoms (i.e. Rabies). There has been no evidence that horses can transmit West Nile virus to other horses. However, isolating the sick horse is advised.

Prognosis can range anywhere from fair to grave, depending on the severity of the disease in any particular horse. Many horses are able to recover from the disease. However, if the horse becomes recumbent/down and unable to rise, the mortality rate greatly increases to approximately 60 percent to 80 percent.

The difference between West Nile virus in humans and horses is that there is protection available for horses through vaccination. There is no specific treatment for horses infected with West Nile virus. The main treatment includes supportive care and there is no guarantee that it will be successful depending on the severity of the disease.

If you have an unvaccinated horse, we strongly urge you to vaccinate it, as prevention is both easier and cheaper than treating (possibly unsuccessfully) your horse. Certain vaccines available vaccinate for eastern and Western encephalitis, which also are transmitted by mosquitoes. Even if your horse has been vaccinated against those strains, we recommend vaccinating specifically for West Nile virus. There is no cross protection from the other strains of encephalitis with regard to vaccinations.

Other ways to prevent West Nile virus include reducing the areas where mosquitoes can live and breed. Eliminating standing water is vitally important to reducing the amount of mosquitoes. Examples include standing water in tires, buckets, cans, planters/pots, bird baths, vinyl coverings for grills, etc. Humans are advised to use mosquito repellent products when working outside (i.e. DEET).

In the past, health departments were testing dead birds found in the area. At this time, local health departments are not testing birds as they are already aware the disease is in the area. Reporting dead birds is still recommended because it does help track West Nile virus activity in the county.

For more information, visit the CDC's website at www.cdc.gov/Westnile.

This article was written by Lori Davis, DVM, member of the Ashland County Veterinary Medical Association, and veterinarian at Byland Animal Hospital. The information is provided as a public service. For specific questions about your pet, contact your local veterinarian. If you have an animal question that you would like to see answered in this column, email Askthevet@times-gazette.com.